1. Technical Field
The present invention relates generally to image processing and, in particular, to a method for accelerating the generation and display of volume-rendered cut-away-views of three-dimensional images.
2. Background Description
One approach to rendering volumetric images such as those created by medical imaging modalities like Computed Tomography (CT) or Magnetic Resonance (MR) is composited volume rendering. In this type of rendering, multiple parallel image textured planes are re-sampled (accumulated) from the original volume and then composited (drawn) into the frame buffer starting with the planar texture most distant from the viewer and progressing in depth-sorted order (back-to-front). A blending function defines how a texture is composited to the existing result in the frame buffer. This blending function can take many forms. One example is the MAX( ) functions which result in a type of rendering called a Maximum Intensity Projection.
Every time the viewing position is changed, the positions and/or orientations of these planar textures may change with respect to the change in viewing position and the compositing procedure must be repeated entirely to update the frame buffer. Compositing is usually the most time consuming component of a volume-rendering procedure.
It is often desirable to produce cut-away views of the volume image. In such a view, a plane is intersected with the original volume image and only those voxels in one of the halfspaces defined by the plane are rendered. This plane is referred to as a cut-plane.
Such cut-away views are useful for understanding the internal structures of volume images. In current practice, however, specifying or moving a cut-plane will necessitate re-compositing the volume.
FIG. 1 is a diagram illustrating a diagonal cut-plane intersecting a volume comprised of a set 100 of nine texture planes 1-9, according to the prior art. The halfspace of this plane containing the viewer 104 (designated by an eye) is being cut away. Those portions of textures not to be rendered are denoted by cross-hatched lines. After cutting away the designated portions of the texture planes, the values of the points P1 through P4 are as follows, with the symbol xe2x80x9c+xe2x80x9d denoting the composition operator:
xe2x80x83P1=1+2+3+4+5+6+7+8+9
P2=1+2+3+4+5+6+7+8
P3=1+2+3+4+5+6+7
P4=1+2+3+4+5+6
Re-compositing the texture planes to obtain the cut-away-view costs 30 (9+8+7+6) accesses to the textures and 26 composing operations (8+7+6+5).
Accordingly, it would be desirable and highly advantageous to have a method for generating and displaying volume-rendered cut-away-views of three-dimensional images that do not require re-compositing the volume when specifying or moving a cut-plane.
The present invention is directed to a method for generating and displaying volume-rendered cut-away-views of three-dimensional images.
According to a first aspect of the invention, there is provided a method for accelerating the generation and display of volume-rendered cut-away-views of three-dimensional images. The method includes the step of rendering a three-dimensional image from a set of textured image surfaces. At least one image corresponding to at least one intermediate result of the rendering step is accumulated. The at least one image includes at least one accumulation of at least two of the textured image surfaces. The at least one image is stored in a volume buffer for subsequent rendering of cut-away-views of the three-dimensional image therefrom.
According to a second aspect of the invention, the accumulating step includes the step of accumulating one image for each of the plurality of textured image surfaces.
According to a third aspect of the invention, the accumulating step includes the step of accumulating one image for only some of the plurality of textured image surfaces.
According to a fourth aspect of the invention, the method further includes the step of generating a cut-away-view of the three-dimensional image by intersecting the at least one image with a volume of the three-dimensional image.
According to a fifth aspect of the invention, the method further includes the step of displaying the cut-away-view of the three-dimensional image.
According to a sixth aspect of the invention, the method further includes the step of generating a cut-away-view of the three-dimensional image by re-compositing missing intermediate results from the at least one image.
According to a seventh aspect of the invention, the method further includes the step of displaying the cut-away view of the three-dimensional image.
According to an eighth aspect of the invention, the rendering step includes the step of compositing the set of textured image surfaces to a single frame buffer, and the method further includes the step of configuring the volume buffer to have a same width and a same height as the single frame buffer.
According to a ninth aspect of the invention, the method further includes the step of moving an existing halfspace partition to display a cut-away-view different than an existing cut-away-view of the three-dimensional image by intersecting the at least one image with a volume of the three-dimensional image.
These and other aspects, features and advantages of the present invention will become apparent from the following detailed description of preferred embodiments, which is to be read in connection with the accompanying drawings.